Benthic Algae Research Articles

Marine Benthic Algae of the Eastern Samar Islands of Homonhon, Sulu-an, and Manicani, Philippines

Botanical explorations in the Philippines have been conducted for the most part in easily accessible regions, resulting in fragmentary information that prevents a thorough assessment of its total biological richness. Many insular sites, which are potentially biologically diverse, remain unexplored due to reasons of geographic isolation, weather disturbance, and logistical considerations. To address these gaps and to provide added information on the diversity and distribution of the seaweed flora around the archipelago, we report herein the taxonomy of the marine benthic algae of three islands in Eastern Samar province. Macrobenthic algae were collected in 18 sites in Homonhon, Sulu-an, and Manicani islands in Guiuan. Seaweeds were identified in situ up to the lowest taxonomic level possible and further analyzed in the laboratory. Cluster analysis based on the Jaccard index using the PAST software was used to infer similarities among the sampling sites with respect to the seaweed flora of the newly collected samples. Analysis of similarities and similarity percentage were also used to further support the results of the study. The paper highlights 56 seaweeds (Chlorophyceae: 28 spp.; Phaeophyceae: 11 spp.; Rhodophyceae: 17 spp.) collected in 18 collection sites in Homonhon, Manicani, and Sulu-an Islands in Guiuan, Eastern Samar. All are considered new records to the small islands, whereas 39 are considered new records of species in the Eastern Samar province. Cluster analysis suggests similarities in seaweed flora in the islands, which may be attributed to the substrates and hydrodynamism in the islands. The islands have a relatively diverse seaweed flora, despite its narrow areas highlighting 5% of the total seaweed flora of the country. This paper is the first attempt to provide better documentation of macroalgal communities in remote islands in the Eastern Philippines (Guiuan, Eastern Samar).

Effect of Volcanic Activity on Hydrocarbon-Forming Organisms in Organic-Rich Shale: A Case Study of Dalong Formation in Northwestern Sichuan Basin, China

Hydrocarbon-generating material determines the elemental composition and hydrocarbon-generating potential of kerogens in a source rock, and it is the key material basis to control the hydrocarbon-generating capacity of the source rock. Previous studies have shown that many intervals of high-quality source rocks generally contain a varying number of volcanic ash layers. The impact of these volcanic ash layers on the development of high-quality source rocks has attracted extensive attention. However, these studies mainly focused on the development of hydrocarbon-forming organisms and the preservation of organic matters but rarely dealt with the differential development of hydrocarbon-forming organisms between multiple volcanic ash layers. The Permian Dalong Formation in the northwestern Sichuan Basin, China, is a set of high-quality source rocks with multiple volcanic sedimentary layers. To understand the differential development of hydrocarbon-forming organisms between volcanic ash layers, with the Dalong Formation in the Longfeng quarry section, Guangyuan, the Sichuan Basin as an example, this study analyzes the types of hydrocarbon-generating materials of high-quality source rocks of the Dalong Formation and the reasons why volcanic activities affected the growth of hydrocarbon-forming organisms and explores the impact of volcanic activities on the development of different types of hydrocarbon-forming organisms. The results show that the TOC of the Longfeng quarry section is 0.05%–15.46%, with an average of 4.76%, and the average TOC of the Dalong Formation is as high as 5.16%, which belongs to high-quality source rocks. The hydrocarbon-forming organism association in the Dalong Formation source rocks is mainly composed of floating algae and benthic algae and vertically divided into three parts: a few radiolarians and trace fossils occasionally in the lower part; a large number of radiolarians, calcium spheres, and algal debris in the middle part; and mainly foraminifera and gastropods in the upper part. There are 36 volcanic ash layers in the Dalong Formation of the study area. In the process of volcanic activity, the “fertilization” effect of volcanic ash made the nutrient elements in the volcanic ash enter water, increasing the number of hydrocarbon-forming organisms, causing the differential development of various hydrocarbon-forming organisms, and promoting the formation of reducing water to support the preservation of organic matters. The development of hydrocarbon-forming organisms is controlled by the changes of element types and abundances caused by magmatic properties. The time interval of volcanic activities also has an important impact on the development of hydrocarbon-forming organisms.

Eutrophication thresholds associated with protection of biological integrity in California wadeable streams

Eutrophication is one of the most pervasive stressors impacting streams, often leading to loss of biodiversity or change in natural functions. To protect against these adverse effects, managers can set targets for environmental indicators to limit eutrophication that are likely to maintain high biological integrity. To identify protective management targets, we evaluated the responses of three bioassessment indices (one for benthic macroinvertebrates and two for benthic algae assemblages) to five eutrophication indicators (total nitrogen [TN], total phosphorus [TP], benthic chlorophyll-a [chl-a], benthic ash-free dry mass [AFDM], and percent macroalgal cover [% cover] of the streambed). First, we used a bioassessment data set of 1249 sites in California to create logistic regression models of the likelihood of achieving several biointegrity goals for each index along increasing gradients of each indicator. Then, we evaluated eutrophication thresholds at concentrations corresponding to several relative probabilities (from 50 to 95 %), reflecting a range of policy makers’ potential tolerance for risk of failing to meet biointegrity goals. Finally, we validated the thresholds with relative risk assessment, and identified the lowest validated threshold across the three indices. All eutrophication indicators were significantly associated with increased risks to biointegrity, resulting in a set of validated thresholds for each biointegrity goal. For example, thresholds of 0.24 mg/L TN, 0.05 mg/L TP, 44 mg/m2 benthic chl-a, 2.5 mg/cm2 AFDM, and 26 % cover would achieve index scores above the 10th percentile of reference (a biointegrity goal that has been used in certain regulatory applications) with an 80 % probability. If these thresholds were applied ambient monitoring statewide dataset, TN was the most pervasively exceeded threshold (37 % of sites), particularly within the highly agricultural Central Valley (76 %), although exceedances of TN and AFDM were also common in the urbanized South Coast region (68 % and 72 % of sites, respectively).

New Material of Carbonaceous Compressions from the ∼1.5 Ga Singhora Group, Chhattisgarh Supergroup, India, and their Interpretation as Benthic Algae

The origin, antiquity, and affinity of benthic seaweeds (multicellular algae) in the geological past are shrouded in mystery due to their preservation bias. In this study, we present a new material of well-preserved carbonaceous compression fossils in shale horizons of the Mesoproterozoic (ca. ∼1,500–1,300 Ma) Singhora Group of the Chhattisgarh Supergroup. Eleven distinct taxa, including one new taxon, Palaeoscytosiphon shuklaii, n. gen. et. sp., and one new species, Jiuqunaoella sergeevii, n. sp., are established. Four unidentified morphologies are also reported. Morphologically, the carbonaceous fossils are fan-shaped, palmate, elongated, leaf-like algal thalli with/without holdfast at the base, isolated or dichotomously branched long filaments, along with multicellular reproductive structures. The results of laser Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX) are also presented in support of their biogenicity. Collectively, the preservation mode of the Singhora carbonaceous fossils suggests multicellular algal affinity and adds to a Burgess Shale-type (BST) taphonomic window in the Pre-Ediacaran biosphere.

The Determination of Algae Group as Bioindicator of Water Quality Change Affected by Mercury Release from Artisanal Small-Scale Gold Mining (ASGM)

Artisanal small scale gold mining (ASGM) practices typically use mercury for amalgamation. Near water environments this can degrade water quality and aquatic biota, including algae. Changes in algal communities can reflect water environment disturbance. The aim of this study was to determine if algae can be used as bioindicator of river water quality impacted by ASGM activities. The research was conducted from July to October 2018 at thirty sampling sites along rivers near ASGM areas in several regencies of Indonesia. Composite samples of water and sediment were collected. A plankton net and brushing methods were used to collect planktonic and benthic algae, respectively. The physicochemical parameters of the water and the sediment as well as the dominant algae genera were analyzed statistically with principal component analysis. The results showed that the total mercury concentration in the water ranged from <0.04 to 20 µg.L-1, while in the sediment the maximum value was 13,500 µg.kg-1. The total mercury content in the sediment was negatively correlated with the dominant benthic Navicula at a significance level of p < 0.05. This means that a low density of benthic Navicula can be proposed as a bioindicator of water quality, indicating the increase of mercury pollution in sediment.

Marine Benthic Algal Composition after 45 Years in an Urbanized Bay in Cebu, Philippines

Coastal ecosystems have been seriously impacted by anthropogenic activities, which are compounded by recent climatic and environmental changes. To provide some evidence of these changes, a study of marine benthic algal composition was conducted by comparing historical (1969–1970) and contemporary (2013–2014) collections in Silot Bay in Cebu, Philippines. A quantitative survey revealed a total of 30 species of benthic algae (11 red, nine brown, and 10 green) in the historical collections, whereas only 15 species (four each of red and brown plus seven species of green algae) were accounted in the latter years. This decline in the marine benthic algal composition may be attributed to sedimentation, which is indirectly caused by urbanization and human population increase. Altered environmental conditions inside the Bay may also explain the decline and qualitative changes of algal species composition therein. Continued monitoring of the benthic macroalgal composition and environmental parameters may help document anthropogenic impacts on marine ecosystems. Historical herbarium samples represent a valuable yet underappreciated resource for tracking environmental changes through time.

Nutrient limitation of primary production in rivers along a land use gradient in the Lake Biwa Basin, Shiga Prefecture, Japan

Benthic microalgae (BMA) biomass and community structure in freshwater lotic systems are often limited by inorganic nutrient availability. We examined nutrient limitation of benthic algae biomass and community structure using nutrient diffusing substrates in four rivers along a land use gradient in the Lake Biwa basin, Japan. Ambient in-stream nutrient concentrations were correlated to catchment land use, with the highest nitrogen and phosphorus concentrations being found in rivers draining more forested catchments. Nutrient limitation of primary producer biomass and nutrient-driven changes in community structure were evident in all four rivers, regardless of in-stream nutrient concentrations and surrounding land use. BMA biomass (measured as chlorophyll log-response ratio) exhibited the greatest nutrient limitation in rivers with higher in-stream nutrient concentrations. The relationship to catchment land use was less clear, with the highest nutrient limitation being observed in the catchment with moderate amounts of agricultural and forested land use. Nutrient additions resulted in a shift from dominance by Bacillariophyceae (diatoms) to a mixed Bacillariophyceae-Chlorophyceae (chlorophyte) community in all rivers and this shift was most pronounced in the forested catchments. Changes within the diatom community with nutrient additions were also observed, although the shifts in diatom community within a river in response to nutrient additions were much smaller than the differences in diatom community composition among rivers. Diatom taxa classified as highly motile increased with nutrient additions in all rivers. Our results suggest that primary producer community in rivers may be sensitive to nutrient inputs even in areas with elevated nutrient concentrations and catchments dominated by agricultural land use. There is likely widespread nutrient limitation in rivers of Japan, across both in-stream nutrient and land use gradients and any increases in nutrient loading will likely stimulate benthic algal growth. Our findings highlight the importance of looking at both biomass and species composition to assess ecosystem-level impacts of elevated nutrient levels.

DNA-assisted inventory and community structure of benthic marine algae in Taiping Island (or Itu Aba Island), South China Sea

Taiping Island (also known as Itu Aba Island) is located in the middle of one of the most politically controversial land strips in the South China Sea, thereby imposing a great obstacle for the exploration of marine biodiversity in this area. The goals of this study were to improve our knowledge gap of biodiversity of benthic marine algae (including both seaweeds and cyanobacteria) and to provide basic herbarium and molecular references on their communities. With 199 molecular sequences assisted for species identification, we found 19 orders, 40 families, 68 genera and 121 species in Taiping Island, including those belonging to 34 Chlorophyta species, 9 Ochrophyta species, 62 Rhodophyta species, and 16 cyanobacteria species. Among them, six genera, 14 species were new records for the South China Sea and more than 70% species were considered as new records for Taiping Island. There were also many taxa which may be considered as undescribed species new to science. In this fringing reef island, the species compositions were significantly different between two types of habitats separated by a reef crest. In the Reef Flat Zone, the most common species encountered included members of Caulerpa, Dictyota, Galaxaura and Halimeda. In the Reef Slope Zone, the most common species included members of Corallinales and Peyssonneliales. The nuisance coral-competing seaweeds (Galaxaura divaricata and Ramicrusta texitilis) and the cyanobacterium (Moorea bouillonii) were reported for the first time in Taiping Island. Our expanded DNA barcoding data in Taiping Island provides a greater understanding of the benthic marine algal biodiversity in the South China Sea.

Effect of the properties of long afterglow phosphors on the antifouling performance of silicone fouling-release coating

To improve the static antifouling performance of the fouling-release silicone antifouling coating, blue-green (BG), yellow-green (YG), and sky blue (SB) long afterglow phosphors (LAP) with two kinds of luminescence intensities are added into the silicone coating, respectively, and the LAP/polydimethylsiloxane (PDMS) composite antifouling coating with different colors and luminance was prepared. Using a scanning electron microscope (SEM), X-ray diffractometer (XRD), laser particle size analyzer, and fluorescence spectrometer, the crystal structure, particle size, fluorescence properties, and emission wavelength of LAP were studied. Through laser confocal scanning microscope (CLSM), tensile test, contact angle measurement, photometer, marine bacteria, and boat-shaped benthic diatom attachment test, the surface morphology and roughness, tensile properties, wettability, and surface of the coating were studied energy, fluorescence illuminance, and anti-fouling performance. The results showed that the addition of LAP increased the fracture strength, elastic modulus, and surface free energy of the coatings. Each kind of LAP can improve the performance of PDMS coatings to inhibit the adhesion of marine bacterial biofilm and benthic marine algae. The higher the luminous illuminance, the better the antifouling performance of the coating. The SB coating has the most excellent antifouling performance and in particular, the relative adhesion rate (RAR) of fouling organisms of the SB highlight LAP/PDMS composite antifouling coating is only 37.8 %. This research provides new ideas for the development of new fluorescent antifouling coatings and has a certain enlightening significance for improving the static antifouling performance of fouling-release antifouling coatings (FRC).

A new look at the potential role of marine plastic debris as a global vector of toxic benthic algae

Marine plastic debris provides a significant surface area for potential colonization by planktonic and benthic harmful microalgae and for the adsorption of their toxins. Furthermore, floating plastics may substantially expand the substrate area available for benthic algae in the ocean, intensifying the transfer of potent toxins through pelagic food webs. In this study, we quantify the available surface area of micro- and macroplastics in different oceanic regions and assess the potential role of floating plastics as vectors for the transfer of toxins from three widespread benthic dinoflagellates, Gambierdiscus spp., Ostreopsis cf. ovata and Prorocentrum lima. To avoid bias associated to the occurrence of benthic algae in deep waters, we selected only records from 0 to 100 m depths. We estimate that 26.8 × 1010 cm2 of plastic surface area is potentially available in surface waters of the global ocean, mostly in the size range of large microplastics (1.01–4.75 mm). Based on the distribution of floating plastics and the habitat suitability of the selected microalgal species, the plastic relative colonization risks will be greater in the Mediterranean Sea and in the subtropical and temperate western margins of the oceans, such as the North American and Asian eastern coasts and, to a lesser extent, southern Brazil and Australia. In places where the colonization of O. cf. ovata cells on floating plastic debris has been properly quantified, such as the Mediterranean and southern Brazil, we estimate a colonization potential of up to 2 × 106 cells km−2 of ocean surface during the regular occurrence period and up to 1.7 × 108 cells km−2 during massive blooms of this species. As plastic pollution and harmful benthic algal blooms have both increased substantially over the past decades, we suggest that their interactive effects can become a major and novel threat to marine ecosystems and human health.

Effects of Elevated Temperature on Resources Competition of Nutrient and Light Between Benthic and Planktonic Algae

Climate warming, a serious environmental problem worldwide, is considered a major threat to aquatic ecosystems. A primary feature of climate warming is elevated temperatures which in shallow aquatic ecosystems might affect competition for light and nutrient between benthic algae on the sediment surface and planktonic algae in the water. The outcomes of such competition would not only affect the distribution of primary production, but also determine the fundamental character of shallow aquatic habitats as clear water or turbid water systems. We conducted a mesocosm study to evaluate the effects of elevated temperature on competition between planktonic algae and benthic algae for light and nutrients. We found that elevated temperature increased the concentrations of total nitrogen (TN), total phosphorus (TP), and total suspended solids (TSS) in overlying water and enhanced the growth of planktonic algae (measured as chlorophylla, Chla), but decreased light intensity and benthic algal biomass (Chla). Our results indicate that elevated temperature can increase the growth of planktonic algae and enhance their competitive advantage over the benthic algae in shallow lakes, thereby contributing to eutrophication and a decline in water quality. These findings shed further light on the effects of global warming on aquatic ecosystems.

Impacts of piscicide-induced fish removal on resource use and trophic diversity of lake invertebrates

Chemical eradication of non-native species has become a widely used method to mitigate the potential negative impacts of altered competitive or predatory dynamics on biodiversity and natural ecosystem processes. However, the responses of non-target species can vary from rapid full recovery to delayed or absent recolonization, and little is known about the potential shifts in resource use and trophic diversity of native species following chemical treatments. We used a before-after-control-impact approach to study the effects of rotenone piscicide treatment on abundance and trophic niche of benthic invertebrates in three untreated and three treated lakes in central Norway, the latter group hosting non-native roach (Rutilus rutilus) and pike (Esox lucius) prior to rotenone treatment. Based on community composition data, the relative abundance of invertebrate grazers and collectors decreased while that of predators increased following fish removal in the treated lakes. The stable isotope data indicated minor shifts in resource use of, and trophic diversity among, benthic invertebrate communities. While the predatory dragonfly larvae (Odonata) and grazer snails (Lymnaeidae) showed increased δ13C values indicating increased reliance on littoral benthic algae, the collector mayfly larvae (Leptophlebia) showed decreased δ13C values following fish removal in treated lakes. Grazer snails also showed a shift to a lower trophic position, while the predatory dragonflies and collector mayflies showed no changes in δ15N values following fish removal. The community-level isotopic niches of benthic invertebrates showed no consistent changes, although the sample-size corrected and Bayesian estimates of standard ellipse areas (SEAC and SEAB) slightly increased in two of the three treated lakes due to an increased range in δ15N. In conclusion, our study findings indicate some changes in species assemblages but minor shifts in the resource use and trophic diversity of benthic invertebrate communities following fish removal in rotenone treated lakes.

Reef-associated depositional environments in the lowermost Cretaceous facies (Berriasian) from the Eastern Prebetic domain (South-Iberian Palaeomargin, SE Spain)

The Berriasian carbonate successions cropping out in the shallow-water platform of the easternmost Prebetic Domain (SE Spain) involve reef-associated environments including a diverse epibiota with diceratid representatives unreported so far. Interpretation of different sub-environments suggests a proximal-distal shallow platform transect. In the shallowest nearshore environment, high energy conditions are recorded, with fine-grained bioclasts interbedded with episodes with black pebbles. Subsequently, a more restricted intra-platform environment is represented by oncoidal rudstones with benthic foraminifera, photophilic microencrusters, microbial-type coatings, mud mounds and a rich record of epibenthic biota preserved in life position (diceratid patches, stromatoporoids, and a diverse coral assemblage). This association points to relatively stable and restrictive low-energy conditions in a proximal shallow-water subtidal environment below the fair-weather wave base. Distally, a deeper, opener setting is established. Here, phaceloid and thin-laminated corals are preserved in life position in a calpionellid-rich matrix typifying a mesophotic reefal complex with clear open marine influence. Biostratigraphical analysis performed mainly on benthic foraminifera, algae, diceratids, and coral representatives allows to specify a Berriasian age for these facies. New occurrence data are also reported, such as the oldest record of the coral genus Floriastrea worldwide. The highly diverse coral assemblages reveal a species-level taxonomic divergence in relation with taxa from the same biochore and palaeogeographical domain, supporting the endemic condition for this fauna. The first report of diceratids in the Eastern Prebetic around the J/C transition evokes Heterodiceras as possible precursor of the Cretaceous rudist build-ups developed in the Urgonian platforms in the Prebetic Domain.

Evaluation of the ecological health and food chain on the shores of four River Nile Islands, Egypt

This study was conducted to evaluate the impact of human activities on the ecological health and food chain at the shores of four Nile Islands in Great Cairo including El-Qeratten, El-Waraq, El-Zamalek, and El-Manial. Water quality, bacteria, phytoplankton, benthic algae, zooplankton, macrobenthic invertebrates, and bony fishes were examined at each island shore over two seasons including the lowest and the highest flow (February and July 2020, respectively). The obtained results showed that the average values of most of the chemicals in Nile Island’s water were within the Egyptian water quality limits. Discriminant analysis of physicochemical factors revealed a similarity between El-Waraq and El-Qerateen and between El-Manial and El-Zamalek. El-Qeratten was the most polluted island. It has the highest total and fecal coliform bacteria count (3.155 and 3.050 Log MPN/100 mL, respectively). El-Zamalek shores have the highest phytoplankton (33,582 cells × 104 L−1) and zooplankton count (310,891 organisms × m−3) and phyto-biochemical values. Biochemical analysis of phytoplankton demonstrated the richness of the bulk by protein (> 85% of biomass), indicating that phytoplankton has a high nutritional value. Elevated zooplankton count was recorded at El-Zamalek, which coincided with the peak of phytoplankton abundance. Mollusca were the dominant macrobenthic invertebrates on most of the island’s shores. Bony fishes were represented by 27 species and two crustaceans. The levels of the metals in fish samples were compared with the food safety guideline endorsed by the World Health Organization and Food and Agriculture Organization (WHO/FAO) to evaluate the toxicity level.

Decreased Internal Phosphorus Loading From Eutrophic Sediment After Artificial Light Supplement: Preliminary Evidence From a Microcosm Experiment

Nutrient loading reduction is an essential approach for controlling eutrophication. In addition to external nutrient loading, internal phosphorus (P) loading is usually considered one of the most important factors determining nutrient levels in water. The underwater light climate plays a pivotal role. However, few studies have been reported on the effect of light intensity on P release, and the existing studies have not drawn a definitive conclusion on whether underwater light has a positive or negative effect on P release. To confirm the effect of underwater light on internal P release, a 1-month microcosm experiment was carried out (18 November–15 December 2020) under three light intensities. The P release flux (FP) was significantly higher in the control (no light) group than in the low light group during the first 2 weeks (p = 0.03). No difference among treatments occurred for accumulative FP in the past 4 weeks, although it tended to be higher in the control than in both the low and high light groups (p > 0.05). Spearman rank correlations showed that photosynthetic photon flux density (PPFD) was positively correlated with DO, pH, phytoplankton chlorophyll a (Chl aPhyt) and benthic algae chlorophyll a (Chl aBent). DO was positively correlated with Chl aPhyt and Chl aBent. The results indicate that light may promote the growth of phytoplankton and benthic algae, both of which may increase DO and pH. DO inhibits P release from sediment and pH promotes P release from sediment. Lake-scale studies are needed to fully evaluate its effect under natural conditions, as many other factors (e.g., wind or fish disturbance) in natural lakes could regulate P release from sediment.

Paleozoic-Mesozoic turnover of marine biological pump and Mesozoic plankton revolution

<p indent="0mm">The evolution of deep-time marine biological pumps (BPs) is critical to our understanding of the processes and mechanisms of the present-day carbon cycle. The Late Paleozoic-Early Mesozoic was a key period for the formation of modern marine biological pumps. Two types of Phanerozoic biological pump have been recognized: Paleozoic (Paleozoic-Middle Triassic) and Modern (Late Triassic-Modern). The Paleozoic-type pump comprises benthic algae and acritarch, whereas the Modern-type pump consists mainly of pelagic plankton. Geological records show that the Permian-Triassic extinction event destroyed the Paleozoic BP. Then, a special BP composed of cyanobacteria and other autotrophic bacteria, briefly appeared during the Permian-Triassic extinction interval. The Modern-type BP consists primarily of pelagic nannoplankton that originated in the Late Triassic. Fossil records suggest that the origin and rapid radiation of nannoplankton (coccoliths and dinoflagellates) during the Late Triassic to Early Jurassic promoted the establishment of modern plankton ecosystem. The rise of pelagic plankton such as dinoflagellates, coccolithophores, and planktonic foraminifers in the Mesozoic is summed up as the Mesozoic plankton revolution. The Mesozoic plankton revolution changed the patterns of marine material cycling and energy flow. The proliferation of nannoplankton accelerated the transfer of material and energy from primary producers to larger consumers and higher trophic levels, increasing the resources available to mesotrophic levels of marine ecosystems. The increased availability of energy resulted in rapid changes in composition, spatial structure, and food chain structures of marine fauna. The resulting “biological arms race” is summarized as the Mesozoic marine animal revolution. The Mesozoic plankton revolution was also the key driver of the Mid-Mesozoic revolution in terms of the regulation of ocean chemistry. Before the Early Jurassic, fluctuations in sea level, ocean area, continental weathering rates, and oceanic calcium ion concentrations produced large perturbations in carbonate deposition and the oceanic carbon cycle, which were only weakly buffered by the ocean. After the Early Jurassic, seawater chemistry changed—With the decrease and stabilization of carbonate saturation due to the transfer of biogenic carbonate from the shallow to the deep marine deposits—Mainly as a result of the rise of nannoplankton and tectonic movement. Changes in seawater chemistry are also reflected in the increased oxygen concentration therein. The oxygen concentration was higher on the Jurassic shelf, likely due to pelagic planktonic algal blooms. The occurrence of phytoplankton increased the efficiency of pelagic biological and carbonate pumps, and the accumulation and dissolution of deep-sea carbonates began to emerge as an important link in the carbon cycle; this improved the buffering capacity of ocean against environmental disturbances. It also provided a stable environment for the creation of modern marine ecosystem, and several oceanic anoxic events that occurred in the Mesozoic did not directly lead to mass extinctions of marine animals, causing only small fluctuations in the diversity of some taxa. Therefore, the Mesozoic plankton revolution is a critical link between the animal and chemical revolutions, and these three processes make up the Mesozoic marine revolution. The origin and evolution of key marine producers and their controlling factors are important topics that need to be studied. However, there are few high-precision studies on the evolution of primary producers and biological pumps during the Late Paleozoic-Early Mesozoic. In addition, the timeline and mechanisms driving the origin of pelagic phytoplankton are key questions that need to be addressed. To solve these problems, the evolution of photosynthetic pigment lineages and the paleogeographic distribution of algae, along with the changes in the size of plankton during the early Mesozoic, require further research attention.

First report of any species of the red algal order Nemaliales from mainland Ecuador: Neoizziella asiatica (Liagoraceae, Rhodophyta)

Abstract The benthic marine algae of the mainland coast of Ecuador are poorly known mainly due to a lack of collections. Currently, DNA barcoding is the preferred method to identify species of benthic marine algae worldwide, as morpho-anatomical characters are inadequate to distinguish many species of macroalgae. We used the red algal barcode rbcL-3P to identify specimens collected in January 2020 from Manabí, Ecuador as Neoizziella asiatica. This is the first member of the red algal order Nemaliales to be reported from the mainland coast of Ecuador and extends the distribution of this alga by 1,100 km to the south from Panama.

Abundance of Benthic Algae in Forestry Watersheds and the Associated Forest Cover Factors

We analyzed the abundance of benthic algae in nine forested headwater watersheds in south-central Chile to study the relationship between the variability of the abundance of benthic algae and physicochemical parameters and forest cover factors. Between 10 November 2015 and 18 August 2016, we sampled benthic algae and physicochemical parameters in the streams and characterized forest cover factors in each of the study watersheds. We found that physicochemical parameters and forest cover factors have contrasting effects on abundance. More specifically, the following observations were made: (1) maximum diversity and abundance occurred in watersheds covered with Pinus radiata, (2) seasonal ranks did not influence the abundance of benthic algae, (3) benthic algae abundance is controlled by rank dissimilarities in type of vegetation, solar radiation, volume, density age, canopy openness, native forest area, plantation area and harvested area, and (4) regression analysis of genera exhibited significant variability with physicochemical parameters (water temperature, pH, ammonium, nitrate, phosphorus, solar radiation) and forest cover factors (volume, density, age, native forest area, plantation area and harvested area); however, these effects were not seen in all genera. Factors related to the benthic algae compartment showed the highest sensitivity to forest cover, emphasizing their value as biological indicators of water quality and stream ecological integrity.

Mapping Benthic Algae and Cyanobacteria in River Channels from Aerial Photographs and Satellite Images: A Proof-of-Concept Investigation on the Buffalo National River, AR, USA

Although rivers are of immense practical, aesthetic, and recreational value, these aquatic habitats are particularly sensitive to environmental changes. Increasingly, changes in streamflow and water quality are resulting in blooms of bottom-attached (benthic) algae, also known as periphyton, which have become widespread in many water bodies of US national parks. Because these blooms degrade visitor experiences and threaten human and ecosystem health, improved methods of characterizing benthic algae are needed. This study evaluated the potential utility of remote sensing techniques for mapping variations in algal density in shallow, clear-flowing rivers. As part of an initial proof-of-concept investigation, field measurements of water depth and percent cover of benthic algae were collected from two reaches of the Buffalo National River along with aerial photographs and multispectral satellite images. Applying a band ratio algorithm to these data yielded reliable depth estimates, although a shallow bias and moderate level of precision were observed. Spectral distinctions among algal percent cover values ranging from 0 to 100% were subtle and became only slightly more pronounced when the data were aggregated to four ordinal levels. A bagged trees machine learning model trained using the original spectral bands and image-derived depth estimates as predictor variables was used to produce classified maps of algal density. The spatial and temporal patterns depicted in these maps were reasonable but overall classification accuracies were modest, up to 64.6%, due to a lack of spectral detail. To further advance remote sensing of benthic algae and other periphyton, future studies could adopt hyperspectral approaches and more quantitative, continuous metrics such as biomass.

Alkalinity and diatom assemblages in lowland streams: How to separate alkalinity from inorganic phosphorus in ecological assessments?

Benthic algae are widely used as ecological indicators of the ecological status of streams because they are widely distributed, they show high species diversity and they respond rapidly to human pressures in particular eutrophication and organic pollution. Recent findings have highlighted that in addition to human pressures, alkalinity may also play a role for community composition as bicarbonate becomes an increasingly important carbon source for photosynthesis when alkalinity increases. With this study, we aimed to elucidate how alkalinity influences the distribution of diatoms in Danish lowland streams, and to explore ifdiatom assemblage patterns can be affected by alkalinity in a way that interferes with the ecological assessment using diatom-based indices. We found that alkalinity affect the benthic algae community in lowland streams and that different species of diatoms were associated with different levels of alkalinity, a finding that might indicate dissimilarities in the efficiency of their HCO3− use. Nitzschia intermedia, Synedra acus, Nitzschia recta, Diatoma tenue, and Nitzschia linearis were associated with high alkalinity, whereas Synedra rumpens, Fragilaria vaucheriae, Psammothidium bioretii, and Gomphonema parvulum were associated with low alkalinity in streams with very low levels of phosphate. We also found that the Danish indicator for ecological status in streams (a combination of two Austrian indices, the Saprobic Index (SID) and the Trophic Index (TID) may exceed levels acceptable for good ecological status in moderate to high alkaline streams despite low phosphate levels. These findings highlight the need for the development of a diagnostic method to disentangle the effects of alkalinity from eutrophication and, additionally, that we need more insight into the autecology of species to interpret ecological assessments to be able to guide management efforts.